Telephone signaling system



y 1936. A. E. woomuFF 2,043,908

TELEPHONE S IGNALING SYSTEM Filed May 24, 1934 INVENTOR ALBERT E.WOODRUFF ATTY.

Patented July 28, 1936 TELEPHONE SIGNALING :SYSTEM Albert E. Woodrufl,Oak Park, 111., assign or to Associated Electric Laboratories, Inc.,Chicago, 111., a corporation of Delaware Application May 24, 1934,Serial No. 727,226

15 Claims.

This invention relates to telephone systems but more particularly toimprovements in signaling arrangements in such systems. One of theprimary objects of the invention is to provide an improved visual andaudible signaling means at a subscribers telephone station. A iurtherobject is to simplify the signaling means and equipment at a telephonesubstation by eliminating the usual ringer coils and gongs and thecondenser and instead utilizing the receiver-of the substation for anaudible signal. A further object resides in providing a neon glow lampat a telephone substation for controlling the signaling. An additionalobject consists in an arrangement employing a neon glow lamp which willpermit signaling current to pass but will not permit voice currents topass, thereby eliminating the transmission losses on a party lineusually caused when ringers are employed at the substation. A furtherobject is to provide an arrangement for removing the neon glow lamp fromthe circuit when the receiver is removed and the telephone placed intalking condition. Other objects and features of the'invention willappear more fully from the detailed description thereof hereinaftergiven.

' In the arrangements of the invention the neon glow lamp is connecteddirectly across the line conductors in series with the'receiver at thesubstation and is shunted out by the substation transmitter when thereceiver is removed. The application of signalingcurrent of audiblefrequency to the line breaks down the lamp and-at the same time actuatesthe receiverto transmit an audible signal or tone. In =order-to breakdown the neon lamp a direct current-battery of suiilcient voltage issuperimposed on the audible frequency current, the direct current beingused both as a means of ionizing-the neon tube and for polarizing thereceiver in case it is of the direct current type without a permanentmagnet. After the lampglows it presents a comparatively low resistancepath to the receiver because, due to the characteristics of these lamps,they will stay operated on a lower voltage than that required to breakthem down.

The invention will be more fully understood from the followingdescription together with the drawing which discloses a preferredembodiment of the invention.

Referring to the drawing, there is indicated diagrammatically for thepurposes of illustration a manual switchboard having cord circuits suchas C. These cord circuits are connected to an operators telephone bymeans of answering key AK, while a ringing key RK is for signalingpurposes. Each subscribers line terminates at the switchboard in a linejack J, and has associated with it the line lamp'L. A single substationon a line is shown at B while a .multi-par'ty line 5 and 6 has a numberof substations, A, A and A connected to it. The substation A as well asthe within the audible range, together with a fairly 15 high directcurrent potential superimposed on the alternating cur-rent, iscontrolled .by the signaling keyi RK in the cord circuit C.

In order to better explain the invention the operations which take placewhen a call is made y will now be pointed out. The subscriber atsubstation B desiring to establish a connection with a subscriber on theparty line 5 and 6, substation A for example, will remove his receiverthereby establishing a direct current circuit path throughthe-transmitter and r-eceiverat substation B, line circuit, contacts ofjack J, and through the line lamp L. The .line lamp L' lights and theoperator answers by .inserting the answering plug P" into jack J therebyextinguishing the lamp L at the ,jack J contacts. The answering key AKis then operated connecting the operators telephone directly with theline conductors of substation B. The relay 9 being connected in thiscircuit operates and closes the circuitfor supervisory lamp AL. It also.furnishes talking current for the telephones from the battery BI'through its windings. The operator upon ascertaining the wishes of thesubscriber at substation B inserts calling plug P of cord G into jack Jthereby separating the jack contacts I and 8 and connecting the cord Cdirectly to the line conductors '5 and 6. The operator now signals thesubstation A by operating the signaling key RK which thereby connects asource of fairlylow voltage alternating current of any desired audiblefrequency, for example from 300 to 1000cycles, through the primary andsecondary windings of transformer TR, comparatively high voltage directcurrent. battery 3-? superimposed upon the alternating current, contactsof key 'RK, plug P and jack J, line conductors 5 and 6, and'through theneon glow lamp N and the receiver R at substation A. The circuitlikewise extends in parallel throughall the other substations A and A.The direct current flowing in the above circuit path ionizes the neonglow lamp N, breaking it down and reducing its resistance so that itremains lighted and provides a low resistance path to the receiver R forthe alternating current flowing in this circuit. The direct current inthis circuit likewise polarizes the receiver R in case it is of thedirect current type not provided with a permanent-magnet. Theillumination of the neon lamp'N will attract the attention of the personat the substation A in case he is some distance from his telephone or incase his hearing is slightly defective. The receiver likewise respondstothe frequency of the alternating current to send out an audible howl ortone to attract the subscribers attention. It will be understood thatthe neon glow lamp as well as the receiver at the other substations Aand A on the same'line, will respond to the signaling current, and theoperator at the switchboard therefore in order to call the substation Aonly, will manipulate the signaling key RK in accordance with aparticular codeof long and short periods of signaling.

In answering the call the receiver R'is'removed from the switchhook S,thereby connecting the transmitter T in series with the receiver Randthe line conductors 5 and 6, while at the same time the transmitter Twhich is of lower resistance shunts the neon glow lamp N from the linecircuit thereby extinguishing it and allowing the receiver R. tofunction normally. The operator restores the signaling key RK and thenher answering keyAK and retires from the connection. Thetelephonesubstation B is now in direct communication with substation A andconversation can proceed, current for talking pur-'- poses beingfurnished for both telephones through the windings of relay 9. Thesupervisory lamp AL therefore remains lighted until both parties havehung up, whereupon the lamp goes out and theoperator withdraws theplugsB and P from jacks J and J to restore the circuits to normal condition.

It will be observed that when the telephones A and B are in directcommunication the receivers.

at substations'A' and A will not interfere with the transmission orpresent a loss in transmission usually occurring with. the ordinarytypes of ring? ing apparatus employed. This is so because the neon glowlamps present an open circuit condi-,.

tion to voice currents on the line and willpermit only high potentialsignaling current to flow th1'ough,them..

The source of high .potential direct'current comprising battery B-?which is'superimposed on the alternating current may satisfactorily be"substituted for a single direct current battery of suflicient voltage tobreak down the neon lamp and at the same time maintain it lighted afterhaving operated. In order, however, .to actuate the. receiver R thisdirect current source would have, to be rapidly interrupted as by abuzzer. Similarly thesource of direct current.B2 could be dispensed withand only an alternating cur-' rent sourceused to break down the neonlamp and maintain it provided it were. of high enough potential, but notto injure the receiver R. It will readily be apparent likewise that neonglow lamps I are constructed to breakdown on different voltages, andtherefore on'the party line illustrated each substation can be providedwith a different neon glow lamp while at the switchboard the operatorwould be provided with'diflerent signaling keyseach connected to adifferent potential of battery. In this manner'the operator would belimited to the exact disclosure but only to the extent of the appendedclaims.

- What iselaim'ed'is:

l. A signalingcircuit for a substation telephone comprising aneonf lampconnected directly in series withQthe telephone receiver when thereceiver is on the switchhook.

2. Asubstation telephone line, a signaling circuit bridged; across saidline at said substation when the receiver is on the switchhook, saidsignaling circuit including a neon lamp and a receiver connected'directly in series therein.

3. A telephone line terminating at a substation, telephoneinstrumentalitiesincluding a receiver at saids'ubstation'and aswitchhook, a signaling circuit'normally connected across said line atsaid substation, before the receivenis removed from the switchhook;including said receiver, and a neon lamp'in series-with said receiveracting as a normally open'valve therefor. 3

4. Ina substation telephone set, a normally closed signaling circuitincluding a neon lamp and the telephone" receiver directly'connected inseries, and means for shunting said neon lamp from said circuit when thereceiver is lifted from the switchhook. Z

5. In a-substation' telephone set, a switchhook,

asignaling circuit at said set including a neon lamp and the telephonereceiver normally con-' ncted in series when the receiver is on theswitchhook,- and-means for connecting the transmitter of said setinshuntof said neon lamp to render it inoperative in said signalingcircuit and for connecting the transmitter in series with thereceiverfor talking purposes; a a

6. In a substatio'rrtelephone set, a signaling cir cuit, a"neongl'owlamp and-telephone receiver connected insaid ignaling" circuit, meansfor transmittingasource of batterypotential to said signalingci'r cuitto break 'down said neon lamp, and means fortransniitting 'a differentsource of current to said circuit to actuate said telephone receiver asa signal.

- '7. In a. substation telephone set, a signaling cir- I cuit, aneonglewiam and telephone-receiver connected to said signaling circuit,means for connectin ga source'o'f direct current potential to saidsignaling circuit to "operate said neon lamp as a visible signal, andmeans for connecting a source of alternating current potential to saidsignaling circuit to operate said telephone receiver as an audiblesignal. 4

8. In a substation telephone set, a signaling circuit includinga neonglow lamp and a telephone receiver, a source of direct current and asource of alternating current, means for connecting the source of 7direct current potential superimposed upon the source of alternatingcurrent to said signalingcircuit to operate said neonlamp as a visiblesignal andSaid receiver as an audible signal. r

9. In a substation telephone set, a signaling circuit. including a neonglow lamp and'a telephone receiver, a source of :direct current and asource ci alternating current, means for connecting said source ofdirect current potential superimposed upon said source of alternatingcurrent to said signaling circuit to operate said neon lamp as a visiblesignal and said receiver as an audible signal, and a shunting circuitincluding a telephone transmitter for removing said neon glow lamp fromsaid signaling circuit.

10. In a party line telephone circuit, a line having a plurality oftelephones thereon, a signaling circuit for each telephone on the line,a neon glow lamp and a receiver in each circuit, means for operating allthe neon lamps and receivers to signal said telephones, means forremoving the neon lamp from the signaling circuit of the desiredtelephone, but maintaining the receiver for talking purposes, the neonlamp of the remaining telephones presenting an open circuit to voicecurrents and preventing transmission losses.

11. In a multi-party telephone line, a line having a plurality oftelephones thereon, a signaling circuit for each telephone on the line,a neon glow lamp and the telephone receiver in each circuit, means fortransmitting signaling current to said line to operate said lamps andreceivers at said telephones as visible and audible signalsrespectively, means for removing said neon lamp at the desired telephonefrom said signaling circuit by shunting it with the telephonetransmitter, said receiver being maintained in said circuit for talkingpurposes, the neon lamps of all other telephones preventing the passageof voice currents and the consequent loss in transmission from thecalled telephone.

12, In a telephone circuit, a telephone receiver arranged to be operatedboth as a telephone instrument and as a signal, and a neon glow lampconnected in series with said receiver in the signaling circuit toprevent the operation of the instrument by talking current and to permitthe operation thereof by signaling current.

13. In a telephone circuit, a telephone receiver operated either as asignal or for telephone purposes, and a neon glow lamp connected to saidreceiver and operated therewith as a signal but rendered inoperativewhen said receiver is used for telephone purposes.

14. In a telephone circuit, means for transmitting signaling current andtalking current over said circuit, a telephone receiver in said circuitresponsive to said signaling current to operate as a call signal andresponsive to said talking current to operate for talking purposes, anda neon glow lamp connected to said telephone receiver for permittingsaid signaling current but not said talking current to operate saidreceiver.

15. In a telephone circuit, means for transmitting signaling current andtalking current over said circuit, a telephone receiver in said circuitresponsive to said signaling current to operate as a call signal andresponsive to said talking current to operate for talking purposes, aneon glow lamp connected to said telephone receiver for permitting saidsignaling current but not said talking current to operate said receiver,and means for rendering said neon glow lamp inoperative and to changesaid circuit to permit the passage of said talking current.

ALBERT E. WOODRUFF.

